This invention relates to gas-testing devices in general and, in particular, to a new and useful testing tube for measuring sodium hydroxide and/or calcium oxide aerosols.
Testing tubes for the quantitative determination of NaOH and/or CaO aerosols have not been heretofore. The reason for this lies in the unclear reaction behavior of the aerosols in the indicating preparations of the testing tubes.
A known method for detecting both volatile and misty arsines uses a testing tube in which filter of inorganic or organic fibrous materials, such as glass-wool, cellulose, or asbestos, is arranged in front of a highly active silica gel layer.
When an air sample is passed through, arsine mists contained therein are retained in the filter, while volatile arsines are fixed by the silica gel. Subsequently, a reagent in the form of a solution of tin-(2)-chloride in concentrated hydrochloric acid is introduced into the testing tube. The mist particles retained by the fiber filter are entrained by the reagent and are flushed toward the silica gel layer. They react with the reagent only on the silica gel in the form of an arsenic deposit. The reaction is thus always observed in the silica gel layer on the silica gel, regardless of whether arsine mists or volatile compounds are present. The reaction takes place directly between the substances to be detected and the indicating reagent. The activity of the silica gel plays a substantial part in the reaction processes. This measuring method can, therefore, only provide qualitative proof of the arsines. In addition, the application of the liquid reaction solution is not harmless (See German Pat. No. 742,689).